The explosives industry makes extensive use of boreholes for blasting in a multitude of applications. In the course of preparing a pattern or series of explosives charges, boreholes are drilled which, on occasions, will fill with water over a period of time due to groundwater migration and other contributing factors. In many types of explosives applications, it is desirable to pump out the water prior to loading the explosives. One of the most cost effective explosives used in the industry is ammonium nitrate (ANFO) and/or water resistant ANFO. The use of ANFO and/or WR ANFO requires the complete dewatering of the borehole prior to being loaded.
In addition, mud and drill cuttings frequently wash into the boreholes from the surface filling a portion of the borehole. Pump systems available to the industry to date are not capable of removing the accumulated mud and drill cuttings without sustaining excessive wear and damage.
Borehole diameter and depths vary according to the application. Borehole diameters range from one inch to over twenty four inches, and are drilled to depths exceeding one hundred feet.
To date, inventors have created several pump systems to dewater boreholes. U.S. Pat. No. 3,788,771 to Atkins (1974) utilizes a submersible rotating air motor for driving a vane type pump. The diameter of this type of pump excludes it from being used in borehole diameters smaller than about four inches. In addition, by the nature of the vane pumping system, wear on the vanes is accelerated due to suspended drill cuttings in the water resulting in loss of efficiency and high operation costs. Also, the inlet and outlet air lines are positioned on the outside of the pump and discharge hose. The irregular outside surface of the pump could cause the pump to hangup on rocks protruding from the borehole wall resulting in wedging the pump in the hole. When this occurs, the pump could be unretrievable and lost. Finally, the pump system by design, is not capable of pumping the accumulations of mud and drill cuttings that frequently accumulate in the bottom of the borehole. Thus, the hole cannot be loaded with explosives to its full drilled depth.
Another method utilizing air as the primary driving source for lifting water from a deep hole or well is shown in U.S. Pat. No. 487,639 to Pohle (1892). This method pressurizes air that is delivered to the bottom of an eduction pipe positioned in the well thereby displacing the head pressure and driving the fluid out. Thereafter, air flow is continued at pressure such that air bubbles are forced to, in effect, act as pistons to lift short columns of water to the top of the pipe. Again, by virtue of size and exterior plumbing, this method is not suitable for repeated lowering and retrieving in boreholes of small size. In addition, the flow rate of this method lacks the flow performance to be economically useful and does not have the ability to transfer water away from the blasting area.
The jet pump method is used in two other U.S. patents. Both units utilize a venturi effect to enhance the desired result. Firstly, U.S. Pat. No. 4,037,991 to Taylor utilizes the Coanda effect to minimize the risk of separation or vapor and/or dissolved gasses from a pumped liquid fuel resulting from low pressure intake to the pump. The pumping and pumped liquid in this instance are of the same composition. This method was developed to transfer jet fuels and does not have an application in dewatering boreholes. And secondly, U.S. Pat. No. 1,038,201 to Rateau (1912) utilizes a fluid recirculating loop applied to an injector fluid flow assist. Since a portion of the fluid must be recirculated at high pressure by a centrifugal jet pump located on the surface, it is not capable of handling solids in the fluid. Also, this system does not self prime. Each time the pump is installed in a borehole, it would have to be primed rendering it unfeasible for borehole dewatering. All of the heretofore inventions suffer from a number of disadvantages for dewatering boreholes for blasting inasmuch as they lack the following requirements:
(A) Pump systems must be able to be inserted into boreholes as small as one and one half inches and easily retrieved with short cycle time to allow immediate loading of explosives before ground water seeps back into the borehole. PA1 (B) The portion of the pump that is inserted into the borehole must be regular in shape so as not to hang-up or wedge itself in the borehole. PA1 (C) The pump system must provide a method for dislodging a pump that becomes wedged or lodged in a borehole so as to enable its retrieval. PA1 (D) Pump systems must be capable of pumping abrasive drill cuttings and mud slurry. PA1 (E) Discharge fluids from the boreholes must be pumped off site to prevent the fluid from migrating back into the boreholes from the surface. PA1 (a) To provide a lightweight portable unit that can easily be moved by hand from borehole to borehole. PA1 (b) To provide a system that will pump liquid, drill cuttings, and mud slurries from small as well as large diameter boreholes to permit loading explosives to the full drilled depth. In addition, to provide a pump that can pump the abrasive drill cuttings and mud slurries without causing accelerated or undue wear on the pump system. PA1 (c) To provide a flexible suction hose portion of the pump that is slim in nature with a relatively smooth outer surface void of any exterior plumbing fixtures. PA1 (d) To provide a pump system that will self prime in a short period of time. PA1 (e) To provide a pump that will pump fluid from a depth of one hundred feet and greater. PA1 (f) To provide a pump that has a reliable means of reversing flow to the suction hose to dislodge materials should the suction hose become wedged in the borehole. PA1 (g) To provide a pump system with a lightweight, flexible suction hose that can be fed into fractured and irregular boreholes, manipulated and retrieved by hand. PA1 (h) To provide a system that will extract the fluid from the suction hose when the borehole is completely dewatered to provide for lifting an empty suction hose from the borehole. PA1 (i) To provide a pump system that is constructed of non-sparking materials that will withstand exposure to the outdoor construction environment as well as incidental contact with corrosive explosives such as ammonium nitrates.